QCD corrections to ZZ production in gluon fusion at the LHC

We compute the next-to-leading-order QCD corrections to the production of two Z-bosons in the annihilation of two gluons at the LHC. Being enhanced by a large gluon flux, these corrections provide a distinct and, potentially, the dominant part of the N3LO QCD contributions to Z-pair production in proton collisions. The gg→ZZ annihilation is a loop-induced process that receives the dominant contribution from loops of five light quarks, that are included in our computation in the massless approximation. We find that QCD corrections increase the gg→ZZ production cross section by O(50%-100%) depending on the values of the renormalization and factorization scales used in the leading-order computation and the collider energy. The large corrections to the gg→ZZ channel increase the pp→ZZ cross section by about 6% to 8%, exceeding the estimated theoretical uncertainty of the recent next-to-next-to-leading-order QCD calculation.